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m5 Model.)

' W. J. GURD.

lnterestflal oulator. No. 229,118. Patented June 22,1880.

KPETERS. PNOTO-UTHOGRAPHER. WASNIMTON. u c.

UNITED STATES PATENT OFFICE.

WILLIAM J. GURD, OF SARNIA, ONTARIO, CANADA.

INTEREST-CA LCULATO R.

SPECIFICATION forming part of Letters Patent No. 229,118, dated June 22,1880.

Application filed April 15, 1880. (No model.)

To all whom it may concern:

Be it known that I, IVILLIAM J. GURD, of Sarnia, in the county ofLambton, in the Province of Ontario, Canada, have invented certain newand useful Improvements in Calculators for Interest and Days; and I dohereby declare that the following is a full, clear, and exactdescription of the same.

The object of this invention is to combine two revolving disks and anindicator, whereby the days from one period to another can be read offby adjustment of the disks, and by the adjustment of a pointer to thedays interest therefor at various rates is indicated along the edge ofthe pointer; and my invention consists in certain improvements in thedetails of construction of the parts, as hereinafter more fully setforth, and pointed out in the claim.

Figure 1 is a plan view. Fig. 2 is a sectional view enlarged. Fig. 3 isa central ver tical section.

In the accompanying drawings, which form a part of this specification, Arepresents an annular disk, and B a center disk, both revolvin gconcentrically, or one may be fixed and the other movable. One of thedisks is inscribed in concentric circles with calculations of interestfrom one to three hundred and sixty-five days, at rates varying fromfour to ten per cent, each rate occupying one circle. Another circle isinscribed with figures of days consecutively from 1 to 365.

O is a pointer pivoted to the center of the inner dial and extendingradially over the outer dial. It is marked with subdivisionscorresponding to the concentric lines of the dial, and inscribed withthe denominations of the rate at which the-interest was calculated,whereby a ready reference is obtained and confusion avoided. In likemanner the subdivisions are marked to denote the days circle of oneyear, and the sum of the interest is read from the disk along the radialedge of the pointer.

The other disk is inscribed concentrically with names of the months anddays of each month, the pointer indicating the circles by marks on thesubdivisions corresponding thereto.

By the adjustment of the disks A and B the number of days from oneperiod of the year to another can be ascertained by placing the day ofthe month from which the period is to be calculated opposite figure l ofthe days in the year, and opposite the day of the month to which theperiod is to be calculated will be found the number of the days whichintervene.

Preferably the sums in the concentric circle are the quotientscalculated-say one hundred dollars at the specified rate of interestfrom one to three hundred and sixty-five days-and any number ofconcentric circles can be inscribed corresponding to the several ratesat which the interest is calculated.

I) (see Fig. 3) represents a base-block for supporting thecalculator,provided with a central hub, F, adapted to fit in a central orifice inthe circular plate E, to the upper face of the outer part of which issecured the ring or disk A. The plate E has a circular central recessadapted to receive the disk B, the upper face of which is flush with thering A. The disk B is attached centrally to the upper, face of the hubF, and is stationary, while we ring A, secured to the outer part of thecircular plate E, revolves with it.

The pointer O is pivoted by means of the screw a centrally in the hub F,and is free to revolve on it, so that it may be swung around to occupyany desired position in determining the interest on any uniform sumatone or more rates for any time, the divisions for rates on the pointerlying opposite thzc calculated interests between the concentric circleson the ring A, the edge of the pointer lying on the desired month andday on the disk B, and also along the interest-spaces between theconcentric circles on the ring A, softhat the interests at differentrates of a uniform sum can be readily read.

hat I claim as my invention is The combination of the fbase D, havingthe central hub, F, plate E, provided with a central orifice and centralcircular recess, revolving ring A, secured to the outer face of saidplate, stationary disk B, flush with the ring attached to the hub andfitting in the recess in the plate, and revolving pointer O, centrallypivoted in the hub, substantially as described, and for the purpose setforth,

- XVILLIAM J. GURD. Witnesses i H. S. SPRAGUE, CHARLES J. HUNT.

